Suppose if a student can't understand English well so what will be our behave with him/her ?how we teach them they can speak or write well?

By reading and listening more for the easy stories.

One of the most interesting methods for teaching English is the Games , Songs and descriptions  

Learning a foreign language is a courageous phenomenon. We should encourage the learner by lending all possible help and passing good remarks from time to time. It is a great moral support to the learner and enables him to overcome different hardships in this process. 

Practice, practice and practice is the only way to perform well. It should be in all the four aspects; reading, writing, speaking and listening.